Grice was of course not into prosody itself, but he found that there are two points:
i. John knew it.
ii. John KNEW it, and not merely believed it.
So, there is an implicature to a suprasegmental.
More importantly, he found that the FLOW of speech should follow the FLOW of meaning which should follow the FLOW of thought!
This he does in his last William James lecture, to the fascination of those who attended it!